A laboratory-scale graywater treatment system based on a membrane filtration and oxidation process — characteristics of graywater from a residential complex

If wastewater can be reused, both the demand for water and the amount of wastewater can be reduced. Wastewater originating from all sources in residential homes other than the toilet is defined as graywater. In this study, graywater was treated through a microfiltration membrane and oxidation process, and the efficiency of the removal of color, turbidity, COD, suspended solids, E. coli, total coliform, Salmonella and Staphylococcus was studied. The treated graywater was reused for purposes other than drinking and bathing, such as fire fighting, water for plants, water for toilets and car washing. The pH of the treated graywater was 7–7.7. The removal efficiency of each factor with the microfiltration membrane was as follows: color (98%); turbidity (99%); COD (99%); suspended solids (99%); E. coli, total coliform, Salmonella and Staphylococcus (30%). Following the membrane filtration process, the efficiency of the removal of each factor using the oxidation process was as follows: color (100%); turbidity (99%); COD (99%); suspended solids (99%); E. coli, total coliform, Salmonella and Staphylococcus (100%). The quantity and quality of the graywater was sufficient to establish a sustainable water circulation system for the reuse of residential graywater. The A2O–MF membrane–OP system showed good treatment capacity. The A2O–MF membrane system could effectively remove COD, turbidity, color, and suspended solids, while OP was effective for the removal of E. coli, total coliform, Salmonella and Staphylococcus.